(a) Field of the Invention
The present invention relates to a gear train of an automatic transmission for a vehicle.
(b) Description of the Related Art
A typical shift mechanism of an automatic transmission utilizes a combination of planetary gear sets. A gear train of such an automatic transmission changes rotating speed and torque received from a torque converter of the automatic transmission, and accordingly changes and transmits the changed torque to an output shaft.
When a transmission has a large number of shift speeds, speed ratios of the transmission can be more optimally designed and therefore a vehicle can have better fuel mileage and better performance.
For a given number of speeds, features of a gear train such as durability, efficiency in power transmission, and size depend a lot on the layout of the planetary gear sets.
A manual transmission with a large number of speeds causes the inconvenience of excessively frequent shifting operations by the driver. Therefore, gear trains with large numbers of shift-speeds lend themselves better to automatic transmissions.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.